<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./js/vue.js"></script>
</head>
<body>
    <div id="box">
        <h1>{{counter}}</h1>
        <button v-on:click="increment">+</button>
        <button @click="increment">+</button>
        <button @click="decrement">-</button>
    </div>
    <script>
        const app = new Vue({
            el : '#box',
            data: {
                counter:0
            },
            methods: {
                increment(){
                    this.counter++
                    console.log(this.counter)
                },
                decrement(){
                    this.counter--
                    console.log(this.counter)
                }
            }
        });
    </script>
</body>
</html>